1. Field
Apparatuses and methods consistent with the present disclosure relate to providing a backlight unit and an apparatus and method for controlling a light-emitting diode (LED) driving circuit, and more particularly, to providing a backlight unit using a light-emitting diode (LED) and an apparatus and method for controlling an LED driving circuit.
2. Description of the Related Art
Liquid crystal displays (LCDs) have been widely used because they are slim and light in weight, consume less power and require low driving voltages, as compared to other displays. However, LCDs do not emit light by themselves, and require additional backlight units to provide light to LCD panels thereof.
Cold cathode fluorescent lamps (CCFLs), light-emitting diodes (LEDs) and the like have been employed as backlight sources for LCDs. CCFLs use mercury and may cause pollution. In addition, CCFLs generally have the disadvantages of low response speed and poor color reproduction and may not be suitable for miniaturization.
LEDs do not use materials that may cause harm to the environment, and may thus be deemed eco-friendly. In addition, LEDs may be impulse-driven. Moreover, LEDs may provide excellent color reproducibility, have an ability to arbitrarily adjust brightness and color temperature by adjusting the amount of light emitted therefrom, and may be suitable for miniaturization. Therefore, LEDs have increasingly been employed as backlight sources for LCD panels.
In a typical boost-type LED driving circuit, a switching metal-oxide semiconductor (MOS) field-effect transistor (FET) may be connected to a ground. Thus, the boost-type LED driving circuit may be easy to be driven. In addition, a dimming MOSFET, which is also driven with the ground, may be added to an LED load terminal, thereby easily controlling the LED at high speed so as to provide high-resolution dimming.
However, the boost-type LED driving circuit requires LED-open protection and LED-short protection. In addition, due to the inherent characteristics of the boost-type LED driving circuit such as a requirement of a high input current, the manufacturing cost of the boost-type LED driving circuit may generally be high.
In a case in which high-resolution dimming is not required, the manufacturing cost of an LED driving circuit may be reduced by applying a low-side buck circuit not using a dimming MOSFET in a peak current control manner without any output current feedback. Peak current control is a technique of switching on a switching MOSFET at a uniform frequency and switching off the switching MOSFET in response to a sensed current reaching the same level as a reference current Iref.
However, this type of method may result in average LED output current fluctuations in case of any load variations or variations in input and output conditions, which is more apparent in a discontinuous conduction mode (DCM), in which a current through an inductor decreases to zero during a switching cycle, than in a continuous conduction mode (CCM), in which the current through the inductor never falls to zero during the switching cycle.
In addition, the CCM may be less suitable for use than the DCM because of its large MOSFET switching loss and a requirement of the use of an inductor with a high inductance.